This invention relates to a cryosurgical probe. It relates more particularly to an improved tip construction for such a probe.
Cryosurgical probes are used to freeze human tissue to effect necrosis, to form scar tissue or to temporarily adhere tissue to the probe tip. These instruments have proved remarkably effective particularly for correcting detached retinas and removing cataracts from the eye.
The tip of the usual pencil-like probe consists of a thin-walled stainless steel tube whose outside diameter is only in the order of 1/16 inch or less. The exposed tip end is closed usually by welding to form a polished spherical surface. That is the working end of the probe which is placed against the tissue.
A small capillary tube extends inside the hollow tip almost to its end and a fluid refrigerant under pressure is supplied to that tube. The fluid expands upon leaving the tube inside the probe tip with the result that the tip end is cooled to a temperature low enough to freeze human tissue.
Conventional pencil-like probes, particularly ophthalmic probes, have an inherent problem which makes some doctors apprehensive about using these instruments. Specifically it has been found that the tip integrity of these probes deteriorates with use. In some cases the deterioration proceeds to the point where the fluid pressure inside the probe tip causes the tip end to separate and project from the rest of the tip. Resultantly, the tip end becomes in effect a small missile which can cause injury to a patient or operating personnel.
The cause of this tip separation is not completely understood. It is believed to be due to physical damage to the tip caused by bending, dents or impacts on the tip. Another possible cause is a chemical reaction between the tip and various impurities which occur if the probe is sterilized by autoclaving without preliminary cleaning. Probe age is another possible factor in the deterioration of probe tip integrity.
Accordingly, it is an object of the present invention to provide a cryosurgical probe whose tip end does not become saparated and project from the probe due to pressurized fluid refrigerant inside the probe tip.
Still another object of the invention is to provide a cryosurgical probe which is safe to use even in delicate eye surgery.
Other objects will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.
In general, the complete separation and projection of the probe tip end from the remainder of the tip is prevented by a small lanyard, one end of which is welded to the tip end and the other end of which is secured to the main body of the probe at a point spaced appreciably from the probe tip. The lanyard is fairly taut so that if the probe end does separate from the remainder of the tip due to refrigerant pressure inside the tip, the lanyard restrains the tip end so that it cannot be projected from the probe and cause possible injury.
Preferably, the lanyard is a wire which is welded to the spherical tip end as that end is formed so that the inclusion of the lanyard does not materially affect the probe's cost or assembly time. Yet the lanyard should drastically reduce the incidence of injury due to flying tip ends. It should especially relieve the anxiety of doctors who use cryosurgical probes, particularly of ophthalmologist performing delicate eye surgery.